Research On Suppressing Errors Of Fringe Projection Profilometry System

With the development of advanced science and technology such as artificial intelligence and intelligent manufacturing,simple the two-dimensional visual information is gradually unable to meet the needs.Three-dimensional data information with depth information is widely used in reverse engineering,mobile payment,intelligent manufacturing and testing,online shopping,VR(Virtual Reality),AR(Augmented Reality),biomedicine.The three-dimensional metrology based on fringe projection profilometry(FPP)has attracted widespread attention due to its advantages such as high accuracy,fast speed,and non-contact.In FPP,the depth of field of the camera in the system is limited and defocusing may occur.The defocus will blur the captured fringe image and thus affect the final reconstruction accuracy.Meanwhile,the difference in phase expansion method will also affect the reconstruction result to a certain extent.In order to solve these two problems in FPP.the following items are studied.1.Review of the key techniques in FPP.Summarizing the research status of optical 3D reconstruction technology and compare various optical 3D reconstruction technologies.The basic principle and phase demodulation method of fringe structed light three-dimensional reconstruction are described.The phase unwrapping technique has a great influence on the accuracy and signal-to-noise ratio of the reconstruction results;the non-impulsive Point Spread Function(PSF)caused by the camera defocusing in the FPP system seriously affects the reconstruction results of the Discontinuity-induced measurement artifact.There are few research results and literature on this issue at present.This article focuses on the research status of phase unwrapping technology and discontinuous region error suppression technology in FPP system which have a great influence on the reconstruction results.2.Studying the phase-altitude calibration technique of FPP system.Study the linear model of the camera pinhole and nonlinear model of camera distortion,principles and basic steps of Zhang's checkerboard calibration method.Study the nonlinear optimization method of the camera model parameters,optimizing linear camera model parameters and calculate camera distortion parameters to reduce reprojection error.Studying reconstruction system height-phase calibration method,and explain the process and steps of the calibration method.3.Fast three-frequency phase unwrapping method.Aiming at the problems of poor robustness of the traditional three-frequency heterodyne method and the three-frequency method,the frequency limit of the fringe is relatively large and the unwrapping speed is slow.Studying the fast three-frequency phase unwrapping method.This method uses the heterodyne principle to effectively reduce the number of traversals of the relationship table,and uses the table construction method to unwrap the phase,which is highly robust and consumes less time.Compared with the three-frequency extrapolation method,this method can reduce the expansion error rate by 90%in areas with more reconstruction errors;the reconstruction time consumption is only 3%of the traditional three-frequency method.4.Research on discontinuity-induced measurement artifact suppression method based on FPP system PSF calibration.The mathematical model of the FPP system is established.According to this model,the PSF in the FPP system is not the ideal impulse function after the camera is out of focus,which is the main reason for the phase error in the discontinuous area.Aiming at the problem that the PSF is not an impulse function in the FPP system and discontinuity-induced measurement artifact is caused and there is a certain change in the PSF in all the measured spaces,proposing a three-dimensional PSF calibration method.The Aiming at the problem that the PSF is not an impulse function in the FPP system and discontinuity-induced measurement artifact is caused and there is a certain change in the PSF in all the measured spaces suppression method based on this calibration method is studied.This method combines the deformed fringe image and the PSF in three-dimensional space,and uses the Deconvolution algorithm to reduce the discontinuity-induced measurement artifact of the object to be measured while enhancing the details of the object to be measured.Experiments show that this method can reduce the discontinuous area error by 70%.